Polyisobutylene/phenol polymers treated with diisocyanates and poly(oxyalkylene)polyols

ABSTRACT

Disclosed herein are block copolymers prepared by polymerizing isobutylene in the presence of an alkyl-substituted phenol as chain transfer agent followed by reaction with a diisocyanate and coupling to a polyoxyalkylene polyol.

BACKGROUND OF THE INVENTION

Block copolymers are well-known items of commerce. Specifically,cationic polymerization of isobutylene is well-known and the use ofvarious polyisocyanates in the formation of block copolymers has beendescribed. Thus, Bauer et al. (Can. J. Chem., 48, 1251 (1970); J. Polym.Sci., A-1, 9, 1451 (1971)) describe cationic polymerization ofisobutylene using alkyl-substituted phenols as chain-transfer agents.U.S. Pat. No. 3,689,593 discloses formation of graft copolymers by vinylpolymerization of an acrylate in the presence of various thiols,alcohols and amines as chain-transfer agents followed by reaction with adiisocyanate. Vinyl monomers are then polymerized in a solution of theisocyanate-terminated copolymers which are coupled to the polyolefin.Rahman et al. (J. Macromol. Sci.-Chem., A13(7), pp. 953-969 (1979))describe block copolymers containing hydrophilic and hydrophobicsequences formed by reacting hydroxy-terminated polybutadiene with anisocyanate-terminated polyethylene oxide.

In U.S. Pat. No. 3,953,406 a mixture of hydrophilic and hydrophobicmaterials (e.g., polybutylene polyols) is admixed with a cross-linkingagent and a diisocyanate followed by curing. U.S. Pat. No. 3,420,915describes polymers formed from phenols and monomeric hydrocarbons whichcan be modified with diisocyanates and hydroxy polyethers. U.S. Pat. No.3,859,382 describes anionic polymerization of olefins containing cyano,ester, nitro or amine groups followed by reaction with a polyisocyanateand subsequently with polyethers, polyamides etc. to form various blockcopolymers. In U.S. Pat. No. 3,989,768 graft copolymers are formedhaving various backbone segments linked to anionically-polymerized sidechains which are said to include isobutylene (col. 9, line). Variouslinkages are formed by the use of isocyanates.

Numerous polyurethane block copolymers containing both hydrophobic andpolyoxyalkylene blocks have also been described, e.g., U.S. Pat. No.3,515,772 (col. 2, lines 11-23; col. 3, lines 11-15 and 38; and col. 6,line 16); U.S. Pat. No. 3,846,163 (col. 8, lines 25 and 28; col. 9, line37; and col. 10, lines 75-col. 11, line 2); and U.S. Pat. No. 3,674,743(cols. 1, 2, 4, 5, 6 and especially col. 6 lines 46-68 and col. 7, line19).

U.S. Pat. No. 3,069,373 describes phenol-terminated polymers which arereaction products of various unsaturated petroleum resins with phenols.The phenol-modified resins are further reacted with polyepoxides. U.S.Pat. No. 4,101,473 describes phenol-blocked isocyanate prepolymers andpolyurethanes prepared therefrom.

While the above patents and journal articles generally use variousagents to couple the copolymer blocks, U.S. Pat. No. 3,418,359 relatesto a process for producing olefin-polyalkylene oxide graft copolymerswhich are directly joined. U.S. Pat. No. 3,376,361 describes blockcopolymers containing oxymethylene groups along with co-monomers such asisobutylene.

U.S. Pat. No. 4,101,434 describes low temperature copolymerization ofisobutylene and styrene in the presence of alkyl phenols. In U.S. Pat.No. 4,107,144 phenolic antioxidants are prepared by admixing a dialkylphenol, a vinylic monomer (e.g., isobutylene), a Friedel Crafts or Lewisacid type catalyst, and an aprotic solvent; polymerizing the monomer ata temperature below 0° C. and stopping the reaction when the polymer hasattained a molecular weight of 1000 to 5000.

DESCRIPTION OF THE INVENTION

The invention is a block copolymer of the following structure: ##STR1##wherein A is a polyisobutylene segment; R is a divalentalkyl-substituted phenyl residue wherein the alkyl substituent groupsare lower alkyl having from 1 to 4 carbons each with the total number ofcarbon atoms being from 2 to 10. R₅ is a divalent aliphatic, aromatic,or cycloaliphatic or cycloalkylene group of from 1 to 36 carbons; and Bis a polyalkylene oxide segment containing oxyethylene, oxypropylene ormixtures thereof.

The copolymer compositions can be employed as ashless oil dispersants,e.g., see U.S. Pat. No. 4,120,804; U.S. Pat. No. 3,697,428; and U.S.Pat. No. 3,948,800. Also, the polymers of the invention can be employedas aqueous dispersing agents for particulate matter. See U.S. Pat. No.4,151,341.

As discussed, in the polymer composition A is a polyisobutylene segmentwhich should have a molecular weight of from about 1000 to 5000 andpreferably from 1000 to 3500. R is a divalent alkyl-substituted aromaticresidue wherein the alkyl substituents have from 2 to 10 carbons andpreferably from 2 to 8. Examples of suitable R groups include phenylresidues having the following formulae: ##STR2## R₁, R₂, R₃ and R₄ areindependently selected from lower alkyl groups having from 1 to 4 carbonatoms, e.g., methyl, ethyl, propyl, butyl, sec-butyl, isobutyl, t-butyland isopropyl.

As discussed, R₅ contains from 1 to 36 carbon atoms and as will bedescribed below, R₅ is the divalent hydrocarbon residue of adiisocyanate. Illustrative of suitable diisocyanates are toluenediisocyanate, 1,6-hexamethylamine diisocyanate, lysine diisocyanate,diphenylmethane-4,4'-diisocyanate and isophorone diisocyanate withtoluene diisocyanate being preferred.

In the above polymer structure, the B group is an oxyalkylene polymerresidue comprising oxyethylene units, oxypropylene units, or mixturesthereof, and can contain small amounts of higher oxyalkylene groups,e.g., up to 20% on a molar basis can be oxybutylene. Preferably, theoxyalkylene residue is hydrophilic, e.g., polyoxyethylene or a blockoxyethylene/oxypropylene copolymer or a random oxyethylene/oxypropylenecopolymer. To achieve satisfactory hydrophilicity the B unit shouldpreferably contain at least 50% on a molar basis of oxyethylene units.While the oxyalkylene polymer is generally essentially linear, branchedpolymers can also be employed, e.g., the reaction product oftrimethyllol propane, glycerol, triethanol amine or other suitableinitiators (functionality of 3 or greater) with ethylene oxide,propylene oxide or mixtures thereof. The molecular weight of thepolymeric B residue is from 1000 to 5000 and preferably from 2000 to4000 as determined by vapor pressure osmometry or by gel permeationchromatography.

The polymer composition of the invention is prepared by cationicallypolymerizing isobutylene in the presence of an alkyl-substituted phenol,a Lewis acid catalyst or Friedel-Crafts catalyst, and an organic liquidto produce a phenol-terminated polymer. The phenol-terminated polymer isreacted with a diisocyanate and optionally a catalyst by a condensationreaction to form an isocyanate-terminated polymer. Subsequently theisocyanate-terminated polymer is reacted with a polyoxyalkylene polyol,i.e., the polyol precursor of the B units described above.

Cationic polymerization of isobutylene in the presence of a phenol isdescribed in R. F. Bauer, R. T. LaFlair, and K. E. Russell, Can. J.Chem., 48, 1251 (1970) and R. F. Bauer and K. E. Russell, J. Polym.Sci., A-1, 9, 1451 (1971) which are hereby incorporated by reference.The cationic polymerization involves dissolving the isobutylene monomerin a suitable organic solvent for the monomer and the phenol. The Lewisacid or Friedel-Crafts catalyst can be added at any convenient timeduring dissolution of the reactants or thereafter. In the reactionmixture, the initial monomer/phenol ratio is from 0.1 to 10 andpreferably from 0.5 to 5; the initial phenol/catalyst molar ratio isfrom 100 to 1000 and the initial concentration of monomer in thereaction mixture (wt. basis) is from 0.2 to 5 mol 1⁻¹ and preferablyfrom 0.5 to 2.5 mol 1⁻¹. The polymerization reaction is allowed tocontinue until the polymer attains a suitable molecular weight, e.g.,from about 5 minutes to about 30 minutes. During polymerization thetemperature is maintained below 0° C. and preferably from -20° to -80°C.

The catalyst is a Lewis acid or a Friedel-Crafts catalyst such asaluminum chloride, stannic chloride/acetic acid, boron trifluoride,titanium chloride or other acid catalyst of this type such as AlBr₃,SbF₅, SbCl₅, PF₅ or FeCl₃. In some cases, particularly with stannicchloride, an acid is desirably added as cocatalyst, e.g., acetic acid, aphenol or HCl; or a small amount of water can be present if an increasedreaction rate is desired. A convenient range for the catalystconcentration is from about 0.05% to about 3% by weight, of the reactionmixture. The concentration range for cocatalyst is usually about 0.05%to about 3% by weight of the reaction mixture.

Suitable aprotic solvents include halogenated hydrocarbons (e.g., methylchloride, methylene chloride, ethyl chloride, trichloroethylene andchloroform), and aliphatic hydrocarbons containing from 4 to 12 carbonatoms and particularly commercially-available mixtures thereof.Generally, the organic solvent should have a boiling point (normalatmospheric) pressure) of from 10° to 100° C. and should be a solventfor both polyisobutylene and the phenol employed.

Suitable phenols are substituted by one or more lower alkyl groupshaving from 1 to 4 carbon atoms with the total number of carbons in thesubstituent groups being from 2 to 10 and preferably 2 to 8. Suitablephenols include those having the following structure: ##STR3## whereinR₁, R₂, R₃ and R₄ are as defined above. Illustrative examples of phenolsinclude 2-sec-butyl phenol, 2,6-dimethyl phenol, 2,6-diisopropyl phenol,2,6-di(2-sec-butyl) phenol, 2,3,4,6-tetramethyl phenol3-ethyl-2,6-diisosbutyl phenol 2,3,5,6-tetraethyl phenol and2,3,6-triisopropyl phenol.

Instead of the single ring phenols, similar alkylsubstituted diphenolsor bisphenols can be used provided there is a vacant 4 or 6 position onone or more benzene rings. Suitable polynuclear phenols include6,6'-dialkyl-2,2'-biphenol, 2,2'-dialkyl-4,4'-isopropylidenediphenol,6,6'-dialkyl-2,2'-methylenediphenol and dialkyl-2,4'-ethylenediphenol.

As discussed above, the phenol appears to act as a chain transfer agentto terminate the polyisobutylene chain, i.e., during polymerization ofthe isobutylene the chains attach to the vacant 4 or 6 position on thephenol nucleus. The phenol also appears to function to some extent as aninitiator for the polymerization reaction. It has been observed thatpolymerizations of isobutylene initiated in the presence of phenols byeither aluminum trichloride or tin tetrachloride yield products ofdecreasing molecular weight as the initial phenol concentration isincreased. Incorporation of phenolic end groups, suggesting chaintransfer by ring alkylation, does occur but the predominant chainbreaking reaction is believed to be expulsion of a proton to form anethylenically-unsaturated end group. Maximum yields for the chainscontaining the phenol end group are about 50%. Reduced temperature andmonomer concentration both increase polymer yields without significantlyaffecting molecular weight or phenol incorporation.

Following the polymerization reaction, the phenol-terminated polymer isfurther reacted with a diisocyanate to cap the hydroxyl group of thephenol. The molar ratio of the diisocyanate to the free phenol hydroxylgroups on the polymer is from 0.5 to 1.5 and preferably 1.0. Suitablediisocyanates are described above.

The isocyanate-terminated polymer is reacted with a polyoxyalkylenepolyol, i.e., the precursor of the B polymer residues described above.The reaction is generally carried out in a suitable solvent for theproduct, e.g., THF. The molar ratio of free NCO contributed by theisobutylene polymer to hydroxyl units contributed by the polyol is from0.5 to 1.5.

EXAMPLE 1

Numerous runs were conducted wherein isobutylene monomer was polymerizedunder vacuum in Pyrex® vessels equipped with Teflon® stirring blades andsyringe caps. Known volumes of solvent and isobutylene were condensedinto the vessels and phenols (2-sec-butyl phenol or 2,6-dimethyl phenol)were added through the syringe caps prior to addition of a Lewis acidcatalyst (AlCl₃). The reactions were terminated after 15 minutes by theaddition of methanol. Where AlCl₃ was used, the reaction mixturecontained 0.72 mole/liter of thionyl chloride to solubilize the AlCl₃.The amount of reactants (in mole/liter of reaction mixture),polymerization temperature and results are set forth in Table I.

                                      TABLE I                                     __________________________________________________________________________    Polymerizations of Iosbutylene (IB) Initiated by Aluminum Trichloride         (AlCl.sub.3)                                                                  in Methylene Dichloride Solution Containing 2-sec-Butyl Phenol (Ph).                            2-sec-butyl                                                     Isobutylene                                                                         AlCl.sub.3                                                                            phenol (10.sup.-2   % Phenol-                               T, °C.                                                                     (mol 1.sup.-1)                                                                      (10.sup.-2 mol 1.sup.-1)                                                              mol 1.sup.-1)                                                                        Yield, %                                                                           --M.sub.w                                                                         --M.sub.n                                                                         Capped Chains                           __________________________________________________________________________    -70 2.4   4.5     0.4    88.6 23,900                                                                            11,800                                                                            2.1                                     -70 2.4   4.5     0.8    81.8 12,100                                                                            5,800                                                                             1.5                                     -70 2.4   4.5     2.0    68.4 17,200                                                                            8,400                                                                             4.7                                     -70 2.4   4.5     4.0    75.6  9,700                                                                            2,900                                                                             5.4                                     -70 2.4   4.5     8.0    55.3  6,400                                                                            2,800                                                                             19.8                                    -70 2.4   4.5     20.0   43.4  7,000                                                                            4,000                                                                             16.5                                    -50 2.4   4.5     4.0    46.9 10,200                                                                            4,400                                                                             7.5                                     -30 2.4   4.5     4.0    27.1  6,700                                                                            3,200                                                                             2.8                                     -10 2.4   4.5     4.0    13.7  5,200                                                                            2,900                                                                             2.3                                     -70 0.7   4.5     4.0    87.5 10,800                                                                            3,000                                                                             4.3                                     -70 4.1   4.5     4.0    53.8 11,400                                                                            4,000                                                                             5.1                                     -50 2.4   0.45    8.0     0.0 --  --  --                                      -70 2.4   2.3     4.0    30.7  9,500                                                                            3,900                                                                             6.6                                     -70 2.4   4.5     10.0(a)                                                                              57.9 11,600                                                                            3,600                                                                             14.7                                    -70 2.4   4.5     5.0(a) 65.8 12,900                                                                            4,400                                                                             8.9                                     -70 2.4   4.5     2.5(a) 66.5 11,300                                                                            4,100                                                                             2.6                                     __________________________________________________________________________     FOOTNOTES                                                                     (a)In these reactions 2,6dimethyl phenol was substituted for 2sec-butyl       phenol.                                                                  

Following polymerization, the phenol-capped polyisobutylene wasreprecipitated from THF solution before drying to constant weight forthe determination of percentage monomer conversion. Polymer molecularweights were estimated by differential refractive index measurements ona Waters Model 244 high-pressure liquid chromatograph equipped withcolumns of 1000, 500 and 100 Aμ-Styragel. THF was used as the mobilephase. A standard GPC calibration for polyisobutylene derived by Kinnedyet al. (J. Poly. Sci. (Chem), 15, 2801 (1977); 16, 243 (1978) was usedto calculate the molecular weights. The distribution of phenol withinpolymer samples was determined by differential U.V. spectroscopy on aWaters Model 440 absorbance detector adjusted to a wavelength of 280 nm.The infrared spectra of polymer samples were measured on a Beckman ModelIR4 spectrophotometer and proton n.m.r. spectra were measured for CDCl₃solutions on a Varian spectrometer.

EXAMPLE 2

Following the procedure of Example 1, isobutylene was again polymerizedusing n-heptane as solvent. The total phenol concentrations weremeasured by U.V. spectroscopy (Cary 14 M spectrophotometer). The initialconcentrations of reactants are as follows: AlCl₃ =4.5×10⁻² mol 1⁻¹ ;isobutylene=2.4 mol 1⁻¹ ; 2-sec-butyl phenol=4.0×10⁻² mol 1⁻¹ andthionyl chloride=0.72 mol 1⁻¹.

                  TABLE II                                                        ______________________________________                                                                         % Phenol-                                    T, °C.                                                                         Yield, %  --M.sub.w                                                                              --M.sub.n                                                                           Capped Chains                                ______________________________________                                        -70     32.8      14,000   4,600 32.5                                         -50     49.3      14,500   7,500 15.7                                         -30     30.8      11,400   5,200 28.3                                         -10     23.0       8,800   4,600 8.6                                          ______________________________________                                    

EXAMPLE 3

Following the procedure of Example 1, isobutylene was polymerized usingmethylene chloride as the solvent and SnCl₄ as Lewis acid catalyst. Nothionyl chloride was employed. After 30 minutes, the reaction wasquenched with methanol. The initial reactant concentrations were;isobutylene=2.4 mol 1⁻¹ and SnCl₄ =0.10 mol 1⁻¹. The concentration ofthe 2-sec-butyl phenol and reaction conditions and results obtained areset forth in Table III below.

                  TABLE III                                                       ______________________________________                                               2-sec-                         % Phenol                                       butyl                          Capped                                  T, °C.                                                                        Phenol   Yield %   --M.sub.w                                                                           --M.sub.n                                                                           Chains                                  ______________________________________                                        -30    0.16     97.1      5,700 2.530 12.0                                    -30    0.24     79.3      5,400 1,400 7.7                                     -50    0.08     100.0     9,400 4,100 11.3                                    -50    0.16     80.6      6,400 3,100 17.6                                    -50    0.24     95.0      8,100 2,800 33.1                                    -50    0.32     100.0     3,700 1,900 32.6                                    -50    0.40     84.8      4,200 2,200 47.0                                    -50    0.80     39.7      1,800   920 26.2                                    -70    0.16     62.3      8,900 5,100 30.9                                    -70    0.24     64.5      5,400 3,200 23.8                                    ______________________________________                                    

EXAMPLE 4

Following the procedure of Example 1, isobutylene was polymerized usingmethylene chloride as solvent and SnCl₄ as the acid catalyst. Thereactions were carried out at a temperature of -50° C. and the initialconcentration of reactants were as follows: isobutylene=2.4 mol 1⁻¹ ;SnCl₄ =0.10 mol 1⁻¹ and 2-sec-butyl phenol=0.08 mol 1⁻¹. Thepolymerization time (i.e., time prior to quenching with methanol), andresults are set forth in Table IV below.

                  TABLE IV                                                        ______________________________________                                        Polymerization                                                                           Yield                   % Phenol-                                  Time, min. %        --M.sub.w                                                                              --M.sub.n                                                                           Capped Chains                              ______________________________________                                        60         100.0    9,700    4,500 11.0                                       30         100.0    9,400    4,100 11.3                                       20         100.0    9,500    4,200 14.6                                       10         100.0    12,200   5,300 15.4                                       ______________________________________                                    

Considering cummulatively the data in Tables I-IV, it should be notedthat isobutylene was polymerized in the presence of SnCl₄ and2-sec-butyl phenol using methylene chloride as solvent but thatpolymerization could not be induced in n-heptane under similarconditions, i.e., a more polar solvent and more acidic catalyst werenecessary as for example the combination of AlCl₃ /n-heptane in Example2 or the AlCl₃ /methylene chloride of Example 1.

Infrared spectra of polyisobutylenes from all Examples displayedidentical features. Two types of double bonds could be discerned. Peaksat 895 cm⁻¹ and 1640 cm⁻¹ indicated the presence of terminalgemdistributed olefins while peaks at 820 cm⁻¹ characteristic oftrisubstituted olefins were also observed (M. St. C. Flett and P. H.Plesch, J. Chem. Soc., 1952, 3355). Proton n.m.r. analyses confirmedthese observations, revealing a broad singlet at δ=4.8 ppm, attributableto geminal protons on a disubstituted terminal olefin, and a peak at 5.1ppm, assigned to the proton on a trisubstituted olefin. Peaks at δ=7.10,6.95, 6.65 and 6.55 ppm, ascribed to the aromatic protons in 2-sec-butylphenol, were also observed.

Determinations of the relative amounts of free and bound phenol in thepolyisobutylene samples were made by GPC using differential U.V.spectroscopy at 280 nm. Differential refractive index measurements werefound to be unreliable for this purpose. Estimates of the concentrationof bound phenol were made by measuring the total phenol concentration byU.V. spectroscopy, assuming the molar extinction coefficient to be thatof the monomeric phenol (2000 l mol⁻¹ cm⁻¹ for 2-sec-butyl phenol and1450 l mol⁻¹ cm⁻¹ for 2,6-dimethyl phenol), and multiplying by thefraction of polymerically bound phenol calculated from the GPC data.

The materials used in carrying out the preceding Examples were preparedas follows: isobutylene was passed through columns of sodium-lead alloyand calcium hydride under vacuum before use. Methylene dichloride andn-heptane were purified by washing with concentrated sulfuric acid,dilute potassium hydroxide solution and distilled water. These solventswere then dried over calcium chloride and calcium hydride andfractionated from calcium hydride. The phenols, thionyl chloride,anhydrous aluminum trichloride and tin tetrachloride were used asreceived.

EXAMPLE 5

Block copolymers were prepared by reacting 5 grams of a mono-phenol(2-sec-butyl phenol) capped polyisobutylene and 0.75 ml toluenediisocyanate (TDI) in THF (50 cc) using 5 drops of stannous octoate ascatalyst. This isocyanate-capped polyisobutylene was then added topolyethylene oxide in THF (10 g, molecular weight approximately 7500 in100 cc solvent) and stirred for 16 hours. Thereafter, the THF wasremoved by evaporation and the solid residue extracted first with apentane (a solvent for polyisobutylene) and then with methanol (asolvent for polyethylene oxide). The residue, which was largely solublein methylene dichloride and THF, is the desired block copolymer ofphenol-capped polyisobutylene coupled to PEG through the TDI linkage.Infrared analysis of the soluble residue indicated the presence of bothpolyisobutylene (methyl group absorbances at 1390 and 1365 cm⁻¹) andpolyethylene oxide (C-O absorbance at 1110 cm⁻¹) moieties. The intrinsicviscosity of methylene dichloride solutions of this material over thetemperature range 10°-40° C. exhibited the maxima and minima that arediagnostic for the presence of block or graft copolymers (Makromol,Chem., 99 275 (1966). Use of an alkali metal catalyst (e.g.,sodium/paraffin dispersion) in preparing the block copolymers was not assuccessful as the method described above, although problems, e.g.,polymer degradation could, in large measure, be due to a lack ofoptional reaction conditions.

EXAMPLE 6 Phenol/TDI Coupling

A phenol-capped polyisobutylene (run 10827-20-12-15) as in Example 5 wasreacted with TDI as follows: 5 g of the polyisobutylene were dissolvedin 50 ml THF; 0.75 ml TDI and 0.2 ml stannous octoate solution wereadded and the solution was brought to reflux. Infrared spectra werescanned in a sodium chloride solution cell at intervals of two hours.After four hours, the isocyanate peak at 2280 cm⁻¹ had been reduced inintensity by about 40 percent. No further reduction had occurred after atotal reaction time of six hours, and 100 ml of a THF solutioncontaining 10 g PEG 7500 was added together with 0.2 ml stannous octoateas catalyst (rather than Na as in Example 5). Refluxing was continuedfor one hour, and the system was then maintained at room temperature fora further 60 hours. At the end of this time the solvent was evaporatedand the crude product subjected to extraction in a Soxhlet apparatus forseven hours with hexane and twelve hours with methanol. The hexanefraction contained polyisobutylene equivalent to the amount charged,indicating that coupling had not occurred. However, this fractiondisplayed strong infrared absorbances at 1720 cm⁻¹, 1605 cm⁻¹ and 3400cm⁻¹ indicative of capping with TDI, while the initial polybutylene hadno absorbance at 1720 cm⁻¹, weak absorbance at 1605 cm⁻¹ and a broadpeak centered at 3500 cm⁻¹. The infrared features are consistent withthe addition of TDI to phenolic endgroups. Coupling can be achieved bymodifying the reaction conditions (e.g., choice of catalyst) as inExample 5.

What is claimed:
 1. A block copolymer having the general structure##STR4## wherein A consists essentially of polyisobutylene segment; R is##STR5## and R₁, R₂, R₃ and R₄ are independently selected from loweralkyl groups having from 1 to 4 carbon atoms and the total of R₁ and R₂is from 2 to 10 carbons; R₅ is a divalent aliphatic, aromatic,cycloaliphatic or cycloalkylene group of 1 to 36 carbons; and B is apolyalkylene polyol segment.
 2. A copolymer as in claim 1 wherein the Asegment has a molecular weight of from 1000 to
 5000. 3. A copolymer asin claim 1 wherein the B segment is polyoxyethylene.
 4. A copolymer asin claim 1 wherein the B segment is polyoxypropylene.
 5. A copolymer asin claim 1 wherein the B segment is a polyoxyethylene/polyoxypropyleneblock copolymer.
 6. A copolymer as in claim 1 wherein the B segment is arandomly copolymerized oxyethylene/oxypropylene copolymer.
 7. Acopolymer as in claim 1 wherein R₅ is a divalent toluene residue.
 8. Acopolymer as in claim 1 wherein R₅ is a divalent 1,6-n-hexyl residue. 9.A copolymer as in claim 1 wherein R₁ and R₂ are methyl.
 10. A processfor preparing the block copolymer of claim 1 which comprises: (A)cationically polymerizing a monomer essentially consisting ofisobutylene in the presence of a phenol, a Lewis acid or Friedel-Craftscatalyst and an organic solvent to produce a phenol-terminated polymer,said phenol having at least two alkyl substituents and being selectedfrom the group consisting of: ##STR6## wherein R₁, R₂, R₃ and R₄ arelower alkyl groups having from 1 to 4 carbon atoms with the total numberof carbons in the substituent groups being from 2 to 10; (B)subsequently reacting the phenol-terminated polymer of (A) with adiisocyanate and optionally a catalyst by a condensation reaction toform an isocyanate-terminated polymer; and (C) subsequently reacting theisocyanate-terminated polymer of (B) with a polyoxyalkylene polyol. 11.A process as in claim 10 wherein the polyoxylakylene polyol ishydrophilic.
 12. A process as in claim 10 wherein the polyoxylakylenepolyol is polyoxyethylene polyol.
 13. A process as in claim 10 whereinthe polyoxalkylene polymer is polyoxypropylene.
 14. A process as inclaim 10 wherein the molar isobutylene/phenol ratio in step (A) is from10 to
 1000. 15. A process as in claim 10 wherein the catalyst in step(A) is SnCl₄.
 16. A process as in claim 10 wherein the catalyst in step(A) is AlCl₃.